Data from laboratory animals and primates suggest that environmental contaminants such as dioxin might be associated with the etiology of endometriosis. The extent to which these findings might be relevant for human females remains elusive and served as the impetus for study. We undertook a study to assess the relation between endometriosis, an estrogen dependent gynecologic disease, and 62 individual polychlorinated biphenyl (PCBs) congeners. We enrolled 84/100 eligible women aged 18-40 years undergoing laparoscopy for study, which included an interview and blood specimen (n=80; 95%). Thirty-two women had visually confirmed endometriosis at laparoscopy while 52 did not. Blood specimens were run in batches of 14 including four quality control samples for toxicologic analysis. Each PCB congener was adjusted for recovery; batch specific reagent blanks were subtracted. All PCB concentrations were log transformed and expressed in ng/g serum first as a sum and then tertiles by purported estrogenic or anti-estrogenic activity of PCB congeners. Using unconditional logistic regression analysis, an elevated risk of endometriosis was observed for the log of total PCBs (OR=1.61; 95% CI =0.63,4.14) after controlling for gravidity, current cigarette smoking and serum lipids. Risk of endometriosis remained elevated for the third tertile of anti-estrogenic PCB congeners (OR=3.11; 95% CI=0.84,11.51) but not estrogenic congeners (OR=1.02; 95%CI=0.29,3.54). These data suggest that anti-estrogenic PCBs may be associated with development of endometriosis.